When to Become a Member
This decision is a personal one, and is sometimes hotly debated on RuneScape fansite forums. The universal answer is whenever you want to and can. A few people suggest waiting until you have fairly high skill levels. Others suggest finishing most of the F2P quests first to build up a respectable skill level. However, many people are confident that you can enjoy being a member at ANY level. It's believed easier to level up as a member, and the many novice-level member quests help considerably. Substantial P2P bank space is also a factor. Being a member provides access to many cool items and skills to make your lower levels more colourful and fun. "Whenever you can talk your family into paying for it" is the most frequent solution!

Where's the best F2P place to mine once I hit 60 - apparently there are tons of bots in the guild (not sure if this is true). At the moment I am mining coal, silver and mithril in the Dwarven Resource Dungeon.